Pelvic Dislocation: Types, Causes, Complications, and Treatment

What are the different types of pelvic dislocation?

Pelvic dislocations are severe, high-energy injuries involving the complete separation of joint surfaces within the pelvic ring, primarily affecting the sacroiliac joints or the pubic symphysis, often resulting in significant instability and potential for life-threatening complications.

Introduction to the Pelvis and its Stability

The pelvis, a robust bony ring structure, serves as the critical link between the axial skeleton (spine) and the appendicular skeleton (lower limbs). It is comprised of three main bones: the two innominate bones (each formed by the fusion of the ilium, ischium, and pubis) and the sacrum. These bones articulate at three key joints: the two sacroiliac (SI) joints posteriorly, where the ilia meet the sacrum, and the pubic symphysis anteriorly, where the two pubic bones connect.

The inherent stability of the pelvic ring is maintained by a complex network of strong ligaments. These include the anterior and posterior sacroiliac ligaments, sacrotuberous, sacrospinous, and iliolumbar ligaments, as well as the superior and inferior pubic ligaments. This ligamentous and bony architecture makes the pelvis exceptionally resistant to injury, meaning dislocations typically only occur under extreme force.

Understanding Pelvic Dislocation

A pelvic dislocation refers to the complete loss of contact between the articular surfaces of a pelvic joint. Unlike more common dislocations (e.g., shoulder or knee), isolated pelvic dislocations are rare. They almost invariably occur as part of a pelvic ring injury, which often includes associated fractures of the pelvic bones. These injuries are typically the result of high-impact trauma, such as motor vehicle accidents, falls from significant heights, or crush injuries.

The primary concern with pelvic dislocations is the disruption of the pelvic ring's integrity, leading to instability. This instability can have severe consequences, including significant internal bleeding (due to proximity to major blood vessels), nerve damage, and injury to internal organs (e.g., bladder, urethra, rectum).

Classification of Pelvic Dislocation

The types of pelvic dislocation are primarily categorized by the specific joint involved and the direction of displacement. It's crucial to understand that these dislocations represent a spectrum of injury severity, often indicating a highly unstable pelvic ring.

Sacroiliac (SI) Joint Dislocation

The sacroiliac joints are robust, relatively immobile joints. Dislocation here signifies a substantial disruption of the powerful ligaments that bind the sacrum to the ilium. SI joint dislocations can be:

• Unilateral vs. Bilateral: Affecting one or both SI joints. Bilateral dislocations are indicative of even higher energy trauma and greater instability.
• Directional Displacements:
  • Anterior Dislocation: The ilium shifts forward relative to the sacrum. This often accompanies an "open-book" type injury where the pubic symphysis also separates.
  • Posterior Dislocation: The ilium shifts backward relative to the sacrum. This is less common but can occur.
  • Superior Dislocation (Vertical Shear): This is one of the most severe forms, where the entire hemipelvis (one side of the pelvic ring) displaces upwards relative to the sacrum. This signifies a complete disruption of the posterior sacroiliac ligaments and often the pubic symphysis, leading to profound instability.
  • Rotational Dislocation: Involves a twisting motion where one part of the ilium rotates relative to the sacrum.

Pubic Symphysis Dislocation (Diastasis)

The pubic symphysis is a cartilaginous joint at the front of the pelvis. A dislocation here, often referred to as diastasis, means the two pubic bones have separated.

• Symmetrical Diastasis: Both sides of the pubic bones separate equally. This is commonly seen in "open-book" injuries where external rotation forces cause the anterior pelvic ring to splay open.
• Asymmetrical Diastasis: One side of the pubic symphysis is displaced more than the other, often indicating a rotational component to the injury.
• Vertical Displacement: One pubic bone displaces vertically relative to the other, often associated with a vertical shear injury of the SI joint.

Combined Pelvic Dislocation

Most severe pelvic injuries involve a combination of disruptions. For instance, a common pattern is a combined SI joint dislocation and pubic symphysis diastasis. This signifies a complete breach of the pelvic ring's anterior and posterior stability. These are often classified further based on the specific mechanisms of injury (e.g., lateral compression, anteroposterior compression, or vertical shear), which dictate the pattern of dislocation and associated fractures.

Associated Injuries and Complications

Due to the high-energy nature of pelvic dislocations and the anatomical density of the pelvic region, associated injuries are common and often life-threatening:

• Hemorrhage: The pelvis is highly vascularized. Major arterial and venous structures (e.g., internal iliac arteries/veins) can be torn, leading to massive, life-threatening internal bleeding.
• Neurological Damage: The sacral plexus, a network of nerves supplying the lower limbs, is located in close proximity to the sacrum. Dislocation can stretch, compress, or tear these nerves, leading to motor weakness, sensory loss, or paralysis in the legs.
• Urogenital Injuries: The bladder, urethra, and rectum are contained within the pelvis. Tears or ruptures of these organs are common, especially in pubic symphysis diastasis or severe vertical shear injuries.
• Fractures: Pelvic dislocations frequently co-occur with pelvic fractures, further complicating the injury and management.
• Skin and Soft Tissue Damage: Open dislocations, where the bone pierces the skin, are rare but carry a high risk of infection.

Diagnosis and Treatment Principles

Diagnosis of pelvic dislocation involves a thorough clinical assessment, including evaluation for shock and associated injuries. Imaging is crucial:

• X-rays: Initial assessment to identify the gross displacement and potential fractures.
• CT Scans: Provide detailed 3D images, essential for fully characterizing the extent of bony and joint disruption, and planning surgical intervention.
• MRI Scans: Useful for assessing ligamentous damage and soft tissue injuries, though less common in acute, unstable settings.

Treatment is typically an emergency, focusing on:

• Resuscitation: Managing hemorrhage and stabilizing the patient's vital signs.
• Pelvic Stabilization: Immediate external stabilization (e.g., pelvic binder, external fixator) to reduce the volume of the pelvic ring, compress bleeding vessels, and provide temporary stability.
• Definitive Management: This almost always involves surgical reduction (realigning the dislocated joint) and internal fixation (using plates, screws, or rods to hold the joint in place) to restore anatomical alignment and stability. Non-surgical management is rarely sufficient for true pelvic dislocations.

Prognosis and Rehabilitation Considerations

The prognosis for pelvic dislocation depends heavily on the severity of the initial injury, the presence of associated complications, and the timeliness and effectiveness of treatment. While modern surgical techniques improve outcomes, patients often face a long and challenging recovery.

• Long-Term Implications: Chronic pain, gait abnormalities, nerve dysfunction, sexual dysfunction, and urinary/fecal incontinence can persist, even after successful surgical repair.
• Rehabilitation: A comprehensive and individualized rehabilitation program is critical. This typically involves:
  • Early Mobilization: As soon as stability allows, to prevent stiffness and muscle atrophy.
  • Strength Training: Focusing on core stability, hip musculature, and lower limb strength.
  • Gait Training: Re-education of walking patterns.
  • Pain Management: To facilitate participation in therapy.
  • Functional Training: Gradually progressing to activities of daily living and, eventually, sport-specific movements if appropriate.

Conclusion

Pelvic dislocations are among the most severe orthopedic injuries, signifying a profound disruption of the body's central skeletal framework. They are not merely joint displacements but indicators of extensive trauma to the entire pelvic ring and its vital contents. Understanding the different types, from sacroiliac joint dislocations to pubic symphysis diastasis, underscores the complexity and life-threatening potential of these injuries. Prompt diagnosis, emergency medical intervention, and expert surgical management followed by rigorous rehabilitation are paramount for optimizing outcomes and mitigating long-term disability.